Effects of cold temperature on starch molecular structure and gelatinization of late-maturity alpha-amylase affected wheat

Abstract

The synthesis of late-maturity alpha-amylase (LMA) occurs when wheat experiences a cold-temperature 'shock' during the post-anthesis, grain-filling period. This markedly increases the high isoelectric point (pI) alphaamylase in wheat grains in susceptible varieties. The affected grain has low Falling Numbers (FN) and is rejected at receival point or downgraded to feed grade, as low FN is associated with inferior end-product quality. However, several studies have reported the lack of correlation between low FN-LMA and end-product quality. Here, we characterize, for the first time, starch molecular structure and gelatinization properties of cold-treated wheat grains; starch structure has significant influence on flour functionality and end-product quality. Results show that the cold-treatment during post-anthesis has minimal effect on starch structure. While there was a small decrease in the gelatinization temperature for every wholemeal flour samples from cold-treated wheat grains, this is unlikely to cause any undesirable effect on end-product. The present findings suggest that the supposition that LMA is a major contributor to inferior end-product quality should be reconsidered.

Late-Maturity Alpha-Amylase in Wheat (Triticum aestivum) and Its Impact on Fresh White Sauce Qualities

“…Thus, the LMA-affected flours had better pasting properties than their controls when LMA was deactivated upon using silver nitrate. It was also shown in previous studies that there was little to no difference in the physical structure of starch granules, molecular starch structure, and other non-polysaccharide components between LMA-affected and sound wheat [4,7,10]. For SEA Condamine, silver nitrate only increased the FV of LMA-affected WF and WWF significantly, whilst other RVA parameters were similar to those of their respective controls.…”

“…These results are consistent to earlier LMA and total α-amylase findings, at which high enzyme content and activity were detected in the bran fraction, which contributed to a greater reduction in the FNs of WWF than that of WF. Unlike the case for PHS, there is no evidence of substantial changes in the starch properties and other non-polysaccharides components of LMA-affected grains [7,10,22]. Thus, any discrepancy in FNs between control and LMA-affected flours is attributed solely to inherent α-amylase.…”

“…Its thickening characteristics are related to the starch granule morphology and α-amylase activity [9]. Previous studies reported no differences in the grain compositions and starch structure between non-LMA-and LMA-affected wheat [7,10]. However, the excessive amount of α-amylase in LMA affected grains drastically reduced flour gelation ability due to starch liquefaction and have very low final viscosities, although it seems to have no detrimental impact on bread quality.…”

Over-Expression of a Wheat Late Maturity Alpha-Amylase Type 1 Impact on Starch Properties During Grain Development and Germination

“…Studies have demonstrated that elevated levels of α-amylase in wheat grain did not impact baking or noodle quality ( Ral et al, 2016 , 2017 ). An additional recent study also showed that LMA had very minor impacts on starch properties ( Neoh et al, 2020 ). It was previously assumed that the physical separation of α-amylase from the starch meant there would be no interaction or effect until milling.…”

“…It was previously assumed that the physical separation of α-amylase from the starch meant there would be no interaction or effect until milling. However, studies to date have involved populations with a limited range of LMA-related low falling numbers ( Newberry et al, 2018 ) or very small sample set with low replication ( Neoh et al, 2020 ), making comparative study on the impact of TaAMY1 on starch properties cumbersome. Due to the difficulty of generating sufficient biological material concomitantly affected by LMA in the same genetic background, the comparative study on the impact of TaAMY1 on starch properties have not been performed to date.…”